1. Field of the Invention
The present invention relates to product irradiation devices and, more particularly, to irradiation devices for irradiating products prior to consumption and/or use and to methods of irradiating products using irradiation devices.
2. Brief Description of the Prior Art
It has become desirable to irradiate various types of products, such as medical products and food products, to enhance the quality of the products prior to consumption and/or use thereof. Irradiation of medical and food products has been recognized as an effective means of sterilizing such products. More typically, irradiation has been used for pasteurization of food products, including meat, poultry, produce, cereal and canned goods, to destroy harmful parasites, bacteria and other pathogens and microorganisms in the food products, thusly increasing their safety for human consumption while not necessarily eradicating all micro-organisms. Irradiated food products have also been found to resist deterioration and to possess longer shelf lives. In the case of produce, such as onions and potatoes, irradiation has been found to inhibit the growth of undesired sprouts on the produce. In the case of meat, the need for irradiation has intensified in view of the prevalence of human disease contracted via consumption of contaminated meat.
In the field of product irradiation, the use of radioactive isotopes, electron beams and X-rays as the sources of radiation has been contemplated. Various devices have been proposed for irradiating products to enhance the quality thereof, as exemplified by U.S. Pat. No. 1,876,737 to Opp, U.S. Pat. No. 3,142,759 to Jefferson et al., U.S. Pat. No. 3,411,002 to Armel, U.S. Pat. No. 3,454,761 to Brunner, U.S. Pat. No. 3,641,342 to Armel et al., U.S. Pat. No. 3,686,502 to Sieber, U.S. Pat. No. 4,066,907 to Tetzlaff, U.S. Pat. No. 4,864,595 to Barrett and U.S. Pat. No. 5,001,352 to Tetzlaff. In particular, the Armel, Tetzlaff (""907) and Barrett patents contemplate the irradiation of foodstuffs, as well as animal feed and medical articles, to effect sterilization, to inhibit deterioration and to destroy bacteria. The Opp patent contemplates the in situ irradiation of vegetation in order to kill parasites. The Opp patent relates to X-ray irradiation while the remainder of the cited patents relate to radioactive isotope irradiation. The subject invention is based on employing radioactive isotopes to irradiate products, as opposed to electron beam (E-beam) or X-ray devices.
Prior art product irradiation devices employing radioactive isotopes possess numerous disadvantages and drawbacks. In particular, such prior art product irradiation devices typically rely on complex transport mechanisms for moving the products past irradiation sources within the irradiation devices. Such complex transport mechanisms typically include moving conveyors, platforms, monorails and/or elevators, for example, disposed in high radiation zones of the product irradiation devices. Such transport mechanisms take up valuable space, undesirably add weight and increase the complexity and cost of the product irradiation devices. In addition, exposure of the transport mechanisms to radiation presents significant maintenance and repair problems related to the impairment or degradation of the transport mechanisms due to radiation exposure and the difficulty involved in accessing the transport mechanisms within the high radiation zones. The transport mechanisms typically include numerous moving mechanical parts that require the presence of lubricants, such as oil or grease, in the high radiation zones, in which case maintenance requirements are significantly increased. Accordingly, prior art product irradiation devices are generally associated with frequent down times for troubleshooting and maintenance, during which normal operation of the product irradiation devices must be suspended.
Another drawback of many prior art product irradiation devices employing radioactive isotopes is that the products being irradiated are moved along complex or circuitous prescribed paths through the irradiation devices. In many prior art product irradiation devices, the products are moved in multiple columns and/or rows, are moved between successive levels or tiers and/or are transferred between different conveyors, platforms or other mechanical structures as they are moved along the prescribed paths. Furthermore, some prior art product irradiation devices require that the products be individually rotated, repositioned or reoriented in addition to being moved in the prescribed paths through the irradiation devices. The complexity of the prescribed paths for the products through the irradiation devices, as well as the mechanical structures associated with moving the products in the prescribed paths and/or rotating, repositioning or reorienting the products individually, greatly increase the risk of malfunction and damage to the products being irradiated. Furthermore, in some prior art product irradiation devices, the products to be irradiated must be placed in special containers or bins prior to entering the irradiation devices, thusly undesirably complicating the irradiation operations and adding to the cost thereof. Many prior art product irradiation devices also require very complex indexing and timing systems to effect movement of the products through the irradiation devices. In order to effect the necessary indexing and timing, many prior art product irradiation devices require the presence of a very large number of products or xe2x80x9cdummyxe2x80x9d products in the irradiation devices.
An additional disadvantage associated with some prior art product irradiation devices is that the product irradiation devices are extremely bulky, heavy and cannot be moved from place to place. In particular, some product irradiation devices are located remote from the sources, such as manufacturing or processing facilities, of the products to be irradiated. This requires that the products to be irradiated be brought to the product irradiation devices rather than the product irradiation devices being brought to the sources of the products. Furthermore, some prior art product irradiation devices have the additional drawback of permitting human access to the interiors of the product irradiation devices via entry and/or exit ports through which the products enter and/or exit the product irradiation devices. In some prior art product irradiation devices, the entry and exit ports are disposed adjacent or close to one another or at substantially the same location on the product irradiation devices, thusly creating the risk that non-irradiated products entering the irradiation devices and irradiated products exiting the irradiation devices will become intermingled or mixed up with one another. Accordingly, some products may be inadvertently passed through the irradiation devices more than once and other products may not be irradiated at all. Some prior product irradiation devices have as a disadvantage the requirement that the irradiation sources be located in a water pool when not in use. Consequently, the sources are undesirably subjected to thermal transients, and complex lifting/lowering devices are needed.
Accordingly, the need exists for a product irradiation device employing radioactive isotopes and wherein the number of moving mechanical parts and the prescribed path for the products through the irradiation device are simplified and minimized while allowing products to be continuously irradiated at or proximate their source with minimal maintenance and repair and without inadvertent intermingling of irradiated and nonirradiated products.
Accordingly, it is a primary object of the present invention to overcome the aforementioned disadvantages of prior product irradiation devices and prior methods of irradiating products using product irradiation devices.
Another object of the present invention is to move products relative to and along a non-moving transport surface within a product irradiation device such that the products are moved past an irradiation source within the product irradiation device.
A further object of the present invention is to utilize only a minimal number of hydraulic actuators to move products in a prescribed path through a product irradiation device.
An additional object of the present invention is to eliminate the presence of moving mechanical parts in a high radiation zone of a product irradiation device.
Yet another object of the present invention is to prevent intermingling or mixing of non-irradiated products entering a product irradiation device and irradiated products exiting the product irradiation device.
It is also an object of the present invention to introduce products to be irradiated into a product irradiation device through an entry opening of the product irradiation device and to discharge irradiated products from the product irradiation device through an exit opening of the product irradiation device, the exit opening being disposed at a location remote from the entry opening.
The present invention has as a further object to introduce products into a product irradiation device, to move the products through the product irradiation device and to discharge the products from the product irradiation device with a maximum external dimension of the products disposed parallel to a plane of an irradiation source within the product irradiation device.
Some of the advantages of the present invention are that personnel requirements for operation and/or maintenance of the product irradiation device are minimized, the product irradiation device does not require any on-site fabrication at the source of the products to be irradiated, standard, transportable enclosures may be used for the product irradiation device, no foundation work is required for the enclosure at the source of the products, no lubricants are present in the high radiation zone, the product irradiation device is entirely self-contained, the product irradiation device is capable of automatic operation with high radiation efficiency, products may be irradiated at their manufacturing or processing facilities, the product irradiation device is relatively small and light weight, the product irradiation device is transportable, products can be irradiated with or without the products being placed in special bins or containers for movement through the irradiation device, mechanical malfunctions are reduced or eliminated, suspensions in normal operation of the product irradiation device are reduced, human access to the interior of the product irradiation device is restricted, redundant interlocks and/or opening/closing mechanisms to prevent human access are not needed, all products receive the same total exposure to radiation, the product irradiation device may be provided with auxiliary equipment for lighting, cooling and/or heating, the auxiliary equipment does not require any supply, such as power, from the source of the products, no personnel are required within the processing facility to handle non-irradiated and irradiated products, personnel requirements are limited to monitoring system operations, periodic maintenance and periodic irradiation source replacement, the irradiation source, once installed, is not moved until replacement is necessary due to radioactive decay, and thermal transients associated with moving irradiation sources into and out of water pools are eliminated.
These and other objects, advantages and benefits are realized with the present invention as generally characterized in a product irradiation device including an enclosure and an irradiator shell disposed in the enclosure. The irradiator shell comprises a wall or walls enclosing an irradiation source and a transport channel. The shell has an inlet port communicating with the transport channel and through which products, prior to being irradiated, are introduced in succession into the transport channel. The shell has an outlet port, different from the inlet port, communicating with the transport channel and through which the products, subsequent to being irradiated, are discharged in succession from the transport channel. The shell has a non-moving transport surface defined by an interior surface or surfaces of the wall or walls and upon which the products are moved through the transport channel past the irradiation source, whereby the products are irradiated. The irradiation source is disposed in a plane, and the transport surface is disposed in a plane perpendicular to the plane of the source. A plurality of hydraulic actuators are provided in or on the shell for moving the products into, through and out of the transport channel in fixed increments with an external dimension of the products parallel to the plane of the source. The enclosure has an entry opening communicating with the inlet port and through which the products are introduced in the transport channel, via the inlet port, from external of the enclosure. The enclosure has an exit opening communicating with the outlet port and through which the products discharged from the transport channel, via the outlet port, are transported to a location external of the enclosure, the exit opening being disposed at a location remote from the entry opening.
A method of irradiating products according to the present invention comprises the steps of introducing products in succession into a transport channel of an irradiator shell via an inlet port of the shell, moving the products relative to and upon a non-moving transport surface of the shell to advance the products through the transport channel in fixed increments such that the products are moved past an irradiation source within the shell and are thereby irradiated, and discharging the products in succession from the transport channel via an outlet port of the shell disposed at a location different from the inlet port.
Other objects and advantages of the present invention will become apparent from the following description of the preferred embodiments taken in conjunction with the accompanying drawings, wherein like parts in each of the several figures are identified by the same reference characters.